Why does Dragonpay respond «Object reference not set to an instance of an object»?

Extensions Dragonpay
1

04

My request was:

amount: "45000.00",
ccy: "PHP",
description: "localhost.com // Dmitry Fedyuk // 000000026",
digest: "5bf96de26f1f8456a9af8618c3824c2857f3d2cb",
email: "admin@mage2.pro",
merchantid: "TESTDMITRY",
txnid: "000000026"
2

It is because the parameters should be passed as GET (in url), not as POST.